The aims of this study are to propose the design bending moment equations and the minimum slab thickness. In the present specifications for highway bridges, the design bending moment of reinforced concrete slabs has been established among limited parameters such as the design concrete strength and the slab thickness. In this study, the design bending moments were considered with various slab thicknesses for rational slab design method from the elastic finite element analysis. Also, the minimum slab thickness was decided based on the bending strength of concrete considering a size-effect law. In the comparison to the specifications for highway bridges and the JSCE design code Part B, it was found that the design bending moment in the direction of distribution bar is necessary to increase.
